Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$42.81	9.513%	$46.8825	$46.88	$46.90	$46.90
Purchase #2	$106.52	10.632%	$117.8452	$117.85	$117.85	$117.80
Purchase #3	$57.53	3.116%	$59.3226	$59.32	$59.30	$59.30
Purchase #4	$105.25	8.296%	$113.9815	$113.98	$114.00	$114.00
Purchase #5	$138.44	10.281%	$152.673	$152.67	$152.65	$152.70
Purchase #6	$189.57	3.272%	$195.7727	$195.77	$195.75	$195.80
Purchase #7	$32.45	9.277%	$35.4604	$35.46	$35.45	$35.50
7 purchase totals =	$672.57		$721.9379	$721.93	$721.90	$722.00